Method for controlling a propeller drive assembly

ABSTRACT

A method of controlling a propeller drive assembly attachable to a hull of a marine vessel, said propeller drive assembly comprising a propeller drive unit and a housing for attachment to a hull of the marine vessel on an inside of the hull. The housing defines an inner space and an opening through which at least a portion of the propeller drive unit is movable into and out of the inner space. The propeller drive assembly comprises a suspension mechanism attached to the housing and configured to suspend the propeller drive unit, wherein the suspension mechanism is adapted to move the propeller drive unit between a stowed position and a deployed position. The method comprises a first step comprising triggering rotation of each propeller shaft such that the respective propeller shaft reaches a respective predetermined rotational position and stops at the respective predetermined rotational position, and a second step comprising triggering movement of the suspension mechanism from the deployed position to the stowed position. Each propeller shaft is provided with a respective propeller, and wherein the respective predetermined position of each propeller shaft is such that each respective propeller is at least partly confined within the inner space of the housing when the propeller drive unit is in the stowed position.

TECHNICAL FIELD

The present disclosure relates to propeller drive systems for marinevessels such as boats and ships.

BACKGROUND

Marine vessels, such as boats and ships, may be provided with motorizedpropulsion devices, such as outboard motors or various types of inboardmotors. The propulsion devices may comprise a propeller drive unit,sometimes referred to as a lower unit or pod, carrying one or morepropeller shafts for carrying a respective propeller.

A common challenge when navigating at sea is to avoid underwaterobstacles hitting the propeller(s). This is especially true fornavigation at shallow waters, and at towing of the marine vessel in suchareas.

Another challenge is to transport the marine vessel over land on atrailer where height constraints from bridges limit the available heightof the marine vessel, forcing the driver to choose longer routes whenthe marine vessel is too high to be able to be transported under aspecific bridge.

SUMMARY

An object of the present disclosure is to reduce the risk of propellerdamage when a marine vessel is towed. Another object of the presentdisclosure is to reduce the size of a propulsion system for a marinevessel, i.e., to provide a propulsion system which takes up less spaceinside marine vessel.

The method is a method of controlling a propeller drive assemblyattachable to a hull of a marine vessel. The propeller drive assemblycomprises a propeller drive unit, sometimes referred to as a lower unitor pod, carrying at least one propeller shaft for carrying a respectivepropeller for rotation about a first rotational axis. The methodcomprises a first step comprising triggering rotation of each propellershaft such that the respective propeller shaft reaches a respectivepredetermined rotational position and stops at the respectivepredetermined rotational position.

The propeller drive assembly further comprises a housing for attachmentto a hull of the marine vessel on an inside of the hull such that thehousing surrounds a first opening of the hull and seals to the hull. Thehousing defines an inner space and is provided with a second openingthrough which at least a portion of the propeller drive unit is movableinto and out of the inner space. The propeller drive assembly comprisesa suspension mechanism attached to the housing and configured to suspendthe propeller drive unit, wherein the suspension mechanism is movablealong a first longitudinal axis of the housing between a stowedposition, in which the propeller drive unit is positioned inside theinner space of the housing, and a deployed position in which at least aportion of the propeller drive unit protrudes outside the housingthrough the second opening. With this hardware in place, the method mayfurther comprise a second step comprising triggering movement of thesuspension mechanism from the deployed position to the stowed position.

Each propeller shaft is provided with a respective propeller, and therespective predetermined position of each propeller shaft is such thateach respective propeller is at least partly, such as fully, confinedwithin the inner space of the housing when the propeller drive unit isin the stowed position.

By combining such rotation of the propeller(s) with the retractablepropeller drive unit, the extent of the propeller below/outside the hullof the marine vessel is reduced, thereby reducing the risk of thepropeller being damaged by underwater objects, such as rocks.

Also, by moving the propeller drive unit to the stowed position, thepropeller is moved in a direction further into the hull of the marinevessel, thus further reducing the extent of the propeller below/outsidethe hull of the marine vessel, thereby further reducing the risk of thepropeller being damaged by underwater objects, such as rocks. Bycombining retraction of the propeller drive unit into the housing, withrotation of the propeller(s) to a respective predetermined position, thereduced extent of the propeller below the hull and/or reduced flowresistance of the portion of the propeller protruding under the hull.

This enables use of a smaller housing of the propeller drive assemblyand thus enables installation of the propeller drive assembly in marinevessels with restricted available space.

The rotation of the propeller(s) to a respective predeterminedrotational position enables control of where propeller blades of thepropeller are positioned when the propellers are not in operation forpropulsion of the marine vessel, such as when the marine vessel isanchored or towed.

For example, the position may be such as to minimize an extent of thepropeller below the vessel, thereby minimizing height of the vessel.Minimizing height of the vessel may be advantageous when moving thevessel through tight passages with limited space available around thevessel, such as when towing the vessel over underground obstacles orduring road transport of the vessel on a trailer, where available heightunder bridges limit what bridges the vessel may be safely transportedunder.

Where the bottom profile of a passage through which the vessel has to betransported only allows passage with the propeller in a specificposition, the predetermined position may be chosen such that the vesselis able to pass the passage by triggering rotation of the propellershaft(s) to respective predetermined positions depending on the bottomcurvature.

The propeller drive assembly may further comprise at least one electricdrive means, for example comprising one or more electric motors. Theelectric drive means are configured to control a rotational position ofeach propeller shaft about said first rotational axis. The first stepcomprises triggering the electric drive means to perform the rotation(s)of the respective propeller shaft(s) to the respective predeterminedrotational position(s).

The use of the electric drive means for control of the respectiverotational position of the propeller shaft(s) enables precise control ofthe rotational position of each propeller shaft. The propeller driveunit may comprise two propeller shafts, each carrying one propeller.

The propellers are rotatable relatively each other about the firstrotational axis such that that a joint projected driving area providedby the propellers in a plane perpendicular to the first rotational axisvaries in response to a relative rotation between a maximum jointprojected driving area and a minimum joint projected driving areatogether defining a joint projected driving area range. The method maycomprise determining the predetermined positions to be such that thejoint projected driving area when the propeller shafts are in theirrespective predetermined positions is within a lower 10% of the jointprojected driving area range or within a lower 5% of the joint projecteddriving area range, or is the minimum joint projected driving area.

The propellers are substantially aligned if the joint projected drivingarea when the propeller shafts are in their respective predeterminedpositions is within a lower 10% of the joint projected driving arearange or within a lower 5% of the joint projected driving area range, oris the minimum joint projected driving area. Such alignment reduces therisk of the propellers striking foreign objects at towing of the marinevessel. Further, such alignment enables less protrusion of thepropellers outside the hull into surrounding water when the propellerdrive unit is in its stowed position.

The propellers may have a same number of blades.

Using two propellers having a same number of blades is advantageoussince the two pairs of propeller blades may be rotated such that theyalign along the first rotational axis and thus minimize the jointprojected driving area, making it easier to pass underwater obstacles.Further, it enables design of a more compact housing for retractablepropeller drive units.

The second step may be performed after, and/or simultaneously with saidfirst step. By rotating the propellers to the predetermined positionbefore, or during movement of the propeller drive unit towards thestowed position, it is possible to position the propeller drive unitcloser to the second opening of the housing whilst maintaining thepropeller inside the inner space of the housing. This enables use of asmaller housing of the propeller drive assembly and thus enablesinstallation of the propeller drive assembly in marine vessels withrestricted available space.

Alternatively, said propeller drive unit comprises two propeller shaftseach carrying one propeller wherein the propellers are rotatablerelatively each other about the first rotational axis such that that ajoint projected driving area provided by the propellers in a planeperpendicular to the first rotational axis varies in response to arelative rotation between a maximum joint projected driving area and aminimum joint projected driving area together defining a joint projecteddriving area range, and wherein the predetermined positions are suchthat the joint projected driving area when the propeller shafts are intheir respective predetermined positions is within a higher 20% of thejoint projected driving area range or within a higher 10% of the jointprojected driving area range, or is the maximum joint projected drivingarea (Amin).

By moving the propeller shafts such that the joint projected drivingarea A is within a higher 20% of the joint projected driving area range,the propellers 4 may be held stationary to provide a great breakingforce for slowing down the marine vessel. For retractable propellerdrive units, such braking of the marine vessel requires the propellerdrive unit to be in its deployed position for maximum breaking effect.

According to a second aspect of the present disclosure, theabove-mentioned objects are also achieved by a control unit forcontrolling a propeller drive assembly attachable to a hull of a marinevessel, said control unit being configured to perform the method,described above.

According to a third aspect of the present disclosure, theabove-mentioned objects are also achieved by a propeller drive systemcomprising a propeller drive assembly and a control unit. The propellerdrive unit carries at least one propeller shaft for carrying arespective propeller for rotation about a first rotational axis. Thecontrol unit is configured to trigger rotation of each propeller shaftsuch that the respective propeller shaft reaches a respectivepredetermined rotational position and stops at the respectivepredetermined rotational position.

The propeller drive assembly further comprises a housing for attachmentto a hull of the marine vessel on an inside of the hull such that thehousing surrounds a first opening of the hull and seals to the hull. Thehousing defines an inner space and the housing is provided with a secondopening through which at least a portion of the propeller drive unit ismovable into and out of the inner space. The propeller drive assemblycomprises a suspension mechanism attached to the housing and configuredto suspend the propeller drive unit, wherein the suspension mechanism ismovable along a first longitudinal axis of the housing between a stowedposition, in which the propeller drive unit is positioned inside theinner space of the housing, and a deployed position in which at least aportion of the propeller drive unit protrudes outside the housingthrough the second opening. The control unit is further configured totrigger movement of the suspension mechanism from the deployed positionto the stowed position.

Each propeller shaft may be provided with a respective propeller,wherein the respective predetermined position of each propeller shaft issuch that each respective propeller is at least partly, such as fully,confined within the inner space of the housing when the propeller driveunit is in the stowed position.

The propeller drive system may further comprise at least one electricdrive means configured to control a rotational position of eachpropeller shaft about said first rotational axis, wherein the controlunit is configured to trigger the electric drive means to perform therotation(s) of the propeller shaft(s) to the respective predeterminedrotational position(s).

The propeller drive system may

The propeller drive unit may comprise two propeller shafts each carryingone propeller.

The propellers are rotatable relatively each other about the firstrotational axis such that that a joint projected driving area providedby the propellers in a plane perpendicular to the first rotational axisvaries in response to a relative rotation between a maximum jointprojected driving area and a minimum joint projected driving areatogether defining a joint projected driving area range. Thepredetermined positions are such that the joint projected driving areawhen the propeller shafts are in their respective predeterminedpositions is within a lower 10% of the joint projected driving arearange or within a lower 5% of the joint projected driving area range, oris the minimum joint projected driving area.

The control unit may be configured to trigger movement of the suspensionmechanism from the deployed position to the stowed position after,and/or simultaneously with, said triggering of rotation of eachpropeller shaft such that the respective propeller shaft reaches arespective predetermined rotational position and stops at the respectivepredetermined rotational position.

According to a third aspect of the present disclosure, theabove-mentioned objects are also achieved by a marine vessel comprisingthe above-mentioned propeller drive system.

According to a fourth aspect of the present disclosure, theabove-mentioned objects are also achieved by a computer program productcomprising program code means for performing the above-mentioned methodwhen said program is run on a control unit.

The above aspects, accompanying claims, and/or examples disclosed hereinabove and later below may be suitably combined with each other as wouldbe apparent to anyone of ordinary skill in the art.

Additional features and advantages are disclosed in the followingdescription, claims, and drawings, and in part will be readily apparenttherefrom to those skilled in the art or recognized by practicing thedisclosure as described herein. There are also disclosed herein acontrol unit, and computer program products associated with the abovediscussed technical effects and corresponding advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-21 show schematic cross-sectional views of various embodimentsof a propeller drive system according to the present disclosure.

FIG. 22 shows a schematic view of an embodiment of a method according tothe present disclosure.

FIGS. 23 a-b and 24 a-b schematically illustrate propeller positions inFIGS. 23 a and 24 a , and in black fill corresponding projected drivesurfaces in a reference plane P in FIGS. 23 b and 24 b.

FIG. 25 is a schematic diagram of a computer system 2500 forimplementing examples disclosed herein.

FIGS. 1-5, 12-16 and 17-21 illustrate embodiments of the propeller drivesystem configured such that their respective propeller drive unit isretractable into the hull of the marine vessel.

FIGS. 6-11 illustrate embodiments of the propeller drive system whichare fixed to the hull and provided with a respective propeller driveunit non-retractably attached to the hull of the marine vessel.

FIGS. 1-8 illustrate embodiments of the propeller drive system providedwith a single propeller.

FIG. 9-21 illustrate embodiments of the propeller drive system providedwith two propeller shafts, each carrying a respective propeller.

FIGS. 1-5 illustrate how a propeller is rotated to be saved fromstriking the bottom at shallow areas, for example when being towed oranchored in such an area.

FIGS. 6-11 illustrate how a propeller is rotated to be saved whenpassing an area with a known bottom curvature, wherein the propeller(s)are rotated to a respective predetermined position chosen such that thepropellers fit with a known recess in the bottom curvature, thusenabling the propellers to be saved from striking the bottom.

DETAILED DESCRIPTION

With reference to the appended drawings, below follows a more detaileddescription of embodiments of the present disclosure cited as examples.

As mentioned above, an object of the present disclosure is to reduce therisk of propeller damage when a marine vessel is towed. Another objectof the present disclosure is to enable design of a compact propulsionsystem for a marine vessel, i.e. a propulsion system which takes up lessspace inside marine vessel.

To achieve these and other object, a propeller drive system 6 and amethod M0 of controlling such a propeller drive system 6 is proposedherein. The method M0 can be used for any suitable propeller drivesystem 6 comprising a propeller drive assembly 1 provided with drivemeans enabling control of the rotational position of one or morepropeller shafts carried by a propeller drive unit 3 of said propellerdrive assembly.

Typically, such drive means could comprise one or more electric motorsoperatively connected to a respective propeller shaft, said electricmotors being of a type operable to stop at one or more predetermineddiscrete rotational positions, for example at one specific rotationalposition or at any one of a plurality of rotational positions.Alternatively, the drive means may comprise any other suitable type ofmotor, which may be combined with one or more stop members movable by anactuator between a position in which the stop member is moved such thatthe respective propeller 4/propeller shaft is free to rotate, to aposition in which the stop member stops the propeller 4 or the propellershaft from further rotation, for example by blocking a propeller hub orpropeller blade to stop movement of the propeller shaft at thepredetermined rotational position P0 a, P0 b.

An exemplary embodiment of the method M0 will be described inconjunction with the exemplary embodiment of the propeller drive system6 illustrated in FIGS. 12-16 . As used in some of the appended figures,reference numeral 16 refers to a sea surface and reference numeral 15refers to a sea bottom or underwater obstacle.

The method M0 is for controlling a propeller drive assembly 1 attachableto a hull 2 of a marine vessel. The propeller drive assembly 1 comprisesa propeller drive unit 3 carrying at least one propeller shaft (notshown) for carrying a respective propeller 4 for rotation about a firstrotational axis 5. As shown in FIG. 22 , the method M0 comprises a firststep M1 comprising triggering rotation of each propeller shaft such thatthe respective propeller shaft reaches a respective predeterminedrotational position P0 a, P0 b and stops at the respective predeterminedrotational position P0 a, P0 b.

The rotation of the propeller shaft(s) to a respective predeterminedrotational position enables control of where propeller blades of thepropeller 4 are positioned when the propellers 4 are not in operationfor propulsion of the marine vessel, such as when the marine vessel isanchored or towed.

The propeller drive assembly may comprise locking means for locking theposition of propeller shaft(s), such that the propellers 4 cannot rotateby the water pressure acting on the propeller 4 at towing of the marinevessel. The locking means may for example comprise a friction breakmovable by an actuator between a breaking position in which the frictionbreak acts on the propeller shaft to prevent it from rotating, and anon-breaking position in which the friction break does not preventrotation of the propeller shaft.

For example, the position may be such as to minimize an extent of thepropeller 4 below the marine vessel, thereby minimizing height of themarine vessel. Minimizing height of the marine vessel may beadvantageous when moving the marine vessel through tight passages withlimited space available around the marine vessel, such as when towingthe marine vessel over underground obstacles or during road transport ofthe marine vessel on a trailer, where available height under bridgeslimit what bridges the marine vessel may be safely transported under.

Where the bottom profile of a passage through which the marine vesselhas to be transported only allows passage with the propeller 4 in aspecific position, the predetermined position may be chosen such thatthe marine vessel is able to pass the passage by rotating the propellershafts to respective predetermined positions depending on the bottomcurvature.

The propeller drive assembly 1 further comprises at least one electricdrive means 7 configured to control a rotational position of eachpropeller shaft about said first rotational axis 5. The first step M1comprises triggering the electric drive means 7 to perform the rotationsof the respective propeller shafts to the respective predeterminedrotational positions P0 a, P0 b.

The use of the electric drive means 7 for control of the respectiverotational position of the propeller shafts enables precise control ofthe rotational position of each propeller shaft.

The method is especially advantageous when used with retractablepropeller drive units 3, such as the one depicted in FIGS. 12-16 .Accordingly, the propeller drive assembly 1 comprises a housing 8 forattachment to a hull 2 of the marine vessel on an inside of the hull 2such that the housing 8 surrounds a first opening 9 of the hull 2 andseals to the hull 2. The housing 8 defines an inner space 10 and whereinthe housing 8 is provided with a second opening 11 through which atleast a portion of the propeller drive unit 3 is movable into and out ofthe inner space 10. The propeller drive assembly 1 comprises asuspension mechanism 12 attached to the housing 8 and configured tosuspend the propeller drive unit 3, wherein the suspension mechanism 12is movable along a first longitudinal axis 13 of the housing 8 between astowed position P1, in which the propeller drive unit 3 is positionedinside the inner space 10 of the housing 8, and a deployed position P2in which at least a portion of the propeller drive unit 3 protrudesoutside the housing 8 through the second opening 11. Accordingly, themethod M0 further comprises a second step M2 comprising triggeringmovement of the suspension mechanism 12 from the deployed position P1 tothe stowed position P2.

By moving the propeller drive unit 3 to the stowed position, thepropeller 4 is moved in a direction further into the hull 2 of themarine vessel, thus further reducing the extent of the propeller 4below/outside the hull 2 of the marine vessel. In other embodiments, thepropeller drive unit 3 may be non-retractable and hence no housing 8 andno suspension mechanism 12 provided.

As shown in FIGS. 12-16 , each of the two propeller shafts is providedwith a respective propeller 4. The respective predetermined position P0a, P0 b of each propeller shaft is such that each respective propeller 4is fully confined within the inner space 10 of the housing 8 when thepropeller drive unit 3 is in the stowed position P1. In otherembodiments of the method, the respective predetermined position P0 a,P0 b of each propeller shaft may alternatively be such that eachrespective propeller 4 is only partly confined within the inner space 10of the housing 8 when the propeller drive unit 3 is in the stowedposition P1.

The propeller drive unit 3 comprises two propeller shafts each carryingone propeller 4.

Each propeller 4 has two blades, but each propeller 4 may alternativelyin other embodiments, have any other suitable number of blades. Further,as an alternative to having a same number of blades on each propeller 4(not limited to two blades), the propellers 4 may alternatively havedifferent number of blades; For example, one propeller 4 may have twoblades and the other propeller 4 three blades.

The propellers 4 are rotatable relatively each other about the firstrotational axis 5 such that that a joint projected driving area Aprovided by the propellers 4 in a plane P perpendicular to the firstrotational axis 5 varies in response to a relative rotation between amaximum joint projected driving area Amax and a minimum joint projecteddriving area Amin together defining a joint projected driving arearange.

The relationship between rotational positions of propellers 4 and jointprojected driving area A is shown in FIGS. 23 a-b and 24 a-b , howeverwith propellers 4 with different blade size. The black area in FIGS. 23b and 24 b depicts the respective joint projected driving area A foreach relative rotational position of the propellers 4.

In this embodiment, the predetermined positions P0 a, P0 b are such thatthe joint projected driving area A when the propeller shafts are intheir respective predetermined positions P0 a, P0 b is within a lower10% of the joint projected driving area range or within a lower 5% ofthe joint projected driving area range, or is the minimum jointprojected driving area Amin.

The propellers 4 are substantially aligned if the joint projecteddriving area when the propeller shafts are in their respectivepredetermined positions is within a lower 10% of the joint projecteddriving area range or within a lower 5% of the joint projected drivingarea range, or is the minimum joint projected driving area. Suchalignment reduces the propellers 4 striking foreign objects at towing ofthe marine vessel. Further, such alignment enables less protrusion ofthe propellers 4 outside the hull 2 into surrounding water when thepropeller drive unit 3 is in its stowed position.

In this embodiment, the second step M2 is performed after said firststep, such that the propeller 4 blades are oriented in the predeterminedpositions P0 a, P0 b before the propeller drive unit 3 is retracted.This way, the housing 8 may be adapted to the predetermined position ofthe propellers 4, as governed by the predetermined positions of thepropeller shafts, such that the housing 8 conforms to the shape of thepropellers 4 when the propeller drive unit 3 is in its stowed positionP1. Accordingly, there is no need to provide extra room in the housing 8for rotation of the propeller shafts to bring them to theirpredetermined positions when the propeller drive unit 3 is in its stowedposition P1. The first step of triggering rotation of the propellershafts is typically made by providing a control signal to the drivemeans such that the drive means rotates the respective propeller shaftto the respective predetermined position P0 a, P0 b.

In the embodiments of the FIGS. 1-22 , a control unit 14 is provided forcontrolling the propeller drive assembly 1, said control unit 14 beingconfigured to perform the method according to any one of claims 1-7.

The control unit 14 may be provided separately from the propeller driveassembly 1 and communicate wirelessly with the propeller drive assembly1 or by wire.

Typically, the propeller drive assembly 1 is provided as part of apropeller drive system 6 comprising the propeller drive assembly 1 andthe control unit 14. This is the configuration used in the embodimentsof the FIGS. 1-22 .

The propeller drive unit 3 carries at least one propeller shaft forcarrying a respective propeller 4 for rotation about a first rotationalaxis 5. The control unit 14 is configured to trigger rotation M1 of eachpropeller shaft such that the respective propeller shaft reaches arespective predetermined rotational position P0 a, P0 b and stops at therespective predetermined rotational position P0 a, P0 b. In thisembodiment, two propeller shafts and two propellers 4 are provided.

The propeller 4 may be provided separately from the propeller drivesystem 6 and such that an installer orders propellers 4 separately basedon a choice made by the installer according to the needs of the marinevessel to which the propeller drive system 6 is to be installed.

The propeller 4 may alternatively be attached to the respectivepropeller shaft already at manufacturing of the propeller drive system6.

The propeller drive assembly 1 may be provided with means for ensuringthe propeller 4 is aligned on each respective propeller shaft in apredetermined relative rotational position with respect to the propellershaft. For example, each propeller shaft may be provided with splinesconfigured to mate with corresponding splines of each respectivepropeller 4 such that the propeller 4 only fits in a specificorientation on the respective propeller shaft.

Alternatively, the control unit 14 may be provided with a calibrationmode where the control unit 14 moves each respective propeller shaft toa predetermined calibration position and stops the propeller shaft atthe predetermined calibration position, waiting for the installer to fitthe propeller 4 such that the propeller 4 is aligned with a reference,such as matching reference marks on the propeller drive unit 3 and thepropeller 4, or simply by aligning the propeller 4 according toinstructions, for example with one blade pointing straight upwards alongthe first longitudinal axis 13. The control unit 14 may also beconfigured to obtain data provided by the installer relating to thedimension and type of propeller(s) 4 installed.

Any other suitable method or means for ensuring that the relativerotational position of each propeller 4 with respect to the rotationalposition of each respective propeller shaft is known, may alternativelybe used instead. For example, sensors could be provided for determiningthe rotational position of the propeller 4 relatively the propellerdrive unit 3, such as a camera-based system configured to determine thetype of propeller 4 and its orientation, optical sensors, orelectro-magnetic sensors sensing proximity of a specific portion of eachrespective propeller 4 to the sensor which is provided on a knownlocation of the propeller drive assembly 1.

The propeller drive system 6 comprises at least one electric drive means7 configured to control a rotational position of each propeller shaftabout said first rotational axis 5. In this embodiment, the electricdrive means 7 comprises two electric motors coupled to both propellershafts via gears such that each motor drives a respective one of thepropeller shafts. In other embodiments, other types of drive means mayalternatively be provided instead of the electric drive means 7.

The control unit 14 is configured to trigger the electric drive means 7to perform the rotations of the propeller shafts to the respectivepredetermined rotational positions P0 a, P0 b.

In this embodiment, the propeller drive assembly 1 further comprises ahousing 8 for attachment to a hull 2 of the marine vessel on an insideof the hull 2 such that the housing 8 surrounds a first opening 9 of thehull 2 and seals to the hull 2. The housing 8 defines an inner space 10and wherein the housing 8 is provided with a second opening 11 throughwhich at least a portion of the propeller drive unit 3 is movable intoand out of the inner space 10. The propeller drive assembly 1 comprisesa suspension mechanism 12 attached to the housing 8 and configured tosuspend the propeller drive unit 3, wherein the suspension mechanism 12is movable along a first longitudinal axis 13 of the housing 8 between astowed position P1, in which the propeller drive unit 3 is positionedinside the inner space 10 of the housing 8, and a deployed position P2in which at least a portion of the propeller drive unit 3 protrudesoutside the housing 8 through the second opening 11.

A similar arrangement is provided in the embodiments shown in FIGS. 1-5and 17-21 .

For such embodiments with propeller drive unit 3 retractable into ahousing 8, the control unit 14 is further configured to trigger movementof the suspension mechanism 12 from the deployed position P2 to thestowed position P1, typically in response to a command obtained by thecontrol unit 14 from an operator of the marine vessel, or from anautomated navigation system.

As shown in FIGS. 12-16 , the respective predetermined position P0 a, P0b of each propeller shaft is such that each respective propeller 4 isfully confined within the inner space 10 of the housing 8 when thepropeller drive unit 3 is in the stowed position P1. In otherembodiments, the respective predetermined position P0 a, P0 b of eachpropeller shaft may alternatively be such that each respective propeller4 is only partly confined within the inner space 10 of the housing 8when the propeller drive unit 3 is in the stowed position P1.

The propeller drive unit 3 comprises two propeller shafts each carryingone propeller 4, wherein the propellers 4 are rotatable relatively eachother about the first rotational axis 5 such that that a joint projecteddriving area A provided by the propellers 4 in a plane P perpendicularto the first rotational axis 5 varies in response to a relative rotationbetween a maximum joint projected driving area Amax and a minimum jointprojected driving area Amin together defining a joint projected drivingarea range, and wherein the predetermined positions P0 a, P0 b are suchthat the joint projected driving area A when the propeller shafts are intheir respective predetermined positions P0 a, P0 b is within a lower10% of the joint projected driving area range or within a lower 5% ofthe joint projected driving area range, or is the minimum jointprojected driving area Amin.

The control unit 14 is configured to trigger movement M1 of thesuspension mechanism 12 from the deployed position P2 to the stowedposition P1 after, and/or simultaneously with said triggering ofrotation M1 of each propeller shaft such that the respective propellershaft reaches a respective predetermined rotational position P0 a, P0 band stops at the respective predetermined rotational position P0 a, P0b.

Alternatively, said propeller drive unit 3 comprises two propellershafts each carrying one propeller 4 wherein the propellers 4 arerotatable relatively each other about the first rotational axis 5 suchthat that a joint projected driving area provided by the propellers 4 ina plane P perpendicular to the first rotational axis 5 varies inresponse to a relative rotation between a maximum joint projecteddriving area Pmax and a minimum joint projected driving area Pmintogether defining a joint projected driving area range. Thepredetermined positions P0 a, P0 b may be such that the joint projecteddriving area when the propeller shafts are in their respectivepredetermined positions P0 a, P0 b is within a higher 20% of the jointprojected driving area range or within a higher 10% of the jointprojected driving area range, or is the maximum joint projected drivingarea (Amin).

By moving the propeller shafts such that the joint projected drivingarea A is within a higher 20% of the joint projected driving area range,the propellers 4 may be held stationary to provide a great breakingforce for slowing down the marine vessel. For retractable propellerdrive units 3, such braking of the marine vessel requires the propellerdrive unit 3 to be in its deployed position for maximum breaking effect.

As shown in FIGS. 1-22 , a marine vessel may be provided, said marinevessel comprising the propeller drive system 6 according to any one ofthe above-mentioned embodiments.

Further, a computer program comprising program code means for performingthe method when said program is run on a control unit 14 may beprovided.

It is to be understood that the present disclosure is not limited to theembodiments described above and illustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the appended claims.

FIG. 25 is a schematic diagram of a computer system 2500 forimplementing the method disclosed herein. The computer system 2500 isadapted to execute instructions from a computer-readable medium toperform these and/or any of the functions or processing describedherein. The computer system 2500 may be connected (e.g., networked) toother machines in a LAN, an intranet, an extranet, or the Internet.While only a single device is illustrated, the computer system 2500 mayinclude any collection of devices that individually or jointly execute aset (or multiple sets) of instructions to perform any one or more of themethodologies discussed herein. Accordingly, any reference in thedisclosure and/or claims to a computer system, computing system,computer device, computing device, control system, control unit,electronic control unit (ECU), processor device, etc., includesreference to one or more such devices to individually or jointly executea set (or multiple sets) of instructions to perform any one or more ofthe methodologies discussed herein. For example, control system mayinclude a single control unit or a plurality of control units connectedor otherwise communicatively coupled to each other, such that anyperformed function may be distributed between the control units asdesired. Further, such devices may communicate with each other or otherdevices by various system architectures, such as directly or via aController Area Network (CAN) bus, etc.

Accordingly, the control unit 14 mentioned in the claims could beimplemented as a computer system 2500 provided locally in the marinevessel, or as a distributed computer system performing the same tasks asthe control unit 14 discussed herein.

The computer system 2500 may comprise at least one computing device orelectronic device capable of including firmware, hardware, and/orexecuting software instructions to implement the functionality describedherein. The computer system 2500 may include a processor device 2502(may also be referred to as a control unit), a memory 2504, and a systembus 2506. The computer system 2500 may include at least one computingdevice having the processor device 2502. The system bus 2506 provides aninterface for system components including, but not limited to, thememory 2504 and the processor device 2502. The processor device 2502 mayinclude any number of hardware components for conducting data or signalprocessing or for executing computer code stored in memory 2504. Theprocessor device 2502 (e.g., control unit) may, for example, include ageneral-purpose processor, an application specific processor, a DigitalSignal Processor (DSP), an Application Specific Integrated Circuit(ASIC), a Field Programmable Gate Array (FPGA), a circuit containingprocessing components, a group of distributed processing components, agroup of distributed computers configured for processing, or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. The processor device may further includecomputer executable code that controls operation of the programmabledevice.

The system bus 2506 may be any of several types of bus structures thatmay further interconnect to a memory bus (with or without a memorycontroller), a peripheral bus, and/or a local bus using any of a varietyof bus architectures. The memory 2504 may be one or more devices forstoring data and/or computer code for completing or facilitating methodsdescribed herein. The memory 2504 may include database components,object code components, script components, or other types of informationstructure for supporting the various activities herein. Any distributedor local memory device may be utilized with the systems and methods ofthis description. The memory 2504 may be communicably connected to theprocessor device 2502 (e.g., via a circuit or any other wired, wireless,or network connection) and may include computer code for executing oneor more processes described herein. The memory 2504 may includenon-volatile memory 2508 (e.g., read-only memory (ROM), erasableprogrammable read-only memory (EPROM), electrically erasableprogrammable read-only memory (EEPROM), etc.), and volatile memory 2510(e.g., random-access memory (RAM)), or any other medium which can beused to carry or store desired program code in the form ofmachine-executable instructions or data structures and which can beaccessed by a computer or other machine with a processor device 2502. Abasic input/output system (BIOS) 2512 may be stored in the non-volatilememory 2508 and can include the basic routines that help to transferinformation between elements within the computer system 2500.

The computer system 2500 may further include or be coupled to anon-transitory computer-readable storage medium such as the storagedevice 2514, which may comprise, for example, an internal or externalhard disk drive (HDD) (e.g., enhanced integrated drive electronics(EIDE) or serial advanced technology attachment (SATA)), HDD (e.g., EIDEor SATA) for storage, flash memory, or the like. The storage device 2514and other drives associated with computer-readable media andcomputer-usable media may provide non-volatile storage of data, datastructures, computer-executable instructions, and the like.

A number of modules can be implemented as software and/or hard-coded incircuitry to implement the functionality described herein in whole or inpart. The modules may be stored in the storage device 2514 and/or in thevolatile memory 2510, which may include an operating system 2516 and/orone or more program modules 2518. All or a portion of the examplesdisclosed herein may be implemented as a computer program product 2520stored on a transitory or non-transitory computer-usable orcomputer-readable storage medium (e.g., single medium or multiplemedia), such as the storage device 2514, which includes complexprogramming instructions (e.g., complex computer-readable program code)to cause the processor device 2502 to carry out the steps describedherein. Thus, the computer-readable program code can comprise softwareinstructions for implementing the functionality of the examplesdescribed herein when executed by the processor device 2502. Theprocessor device 2502 may serve as a controller, or control system, forthe computer system 2500 that is to implement the functionalitydescribed herein.

The computer system 2500 also may include an input device interface 2522(e.g., input device interface and/or output device interface). The inputdevice interface 2522 may be configured to receive input and selectionsto be communicated to the computer system 2500 when executinginstructions, such as from a keyboard, mouse, touch-sensitive surface,etc. Such input devices may be connected to the processor device 2502through the input device interface 2522 coupled to the system bus 2506but can be connected through other interfaces such as a parallel port,an Institute of Electrical and Electronic Engineers (IEEE) 1394 serialport, a Universal Serial Bus (USB) port, an IR interface, and the like.The computer system 2500 may include an output device interface 2524configured to forward output, such as to a display, a video display unit(e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)). Thecomputer system 2500 may also include a communications interface 2526suitable for communicating with a network as appropriate or desired.

The operational steps described in any of the exemplary aspects hereinare described to provide examples and discussion. The steps may beperformed by hardware components, may be embodied in machine-executableinstructions to cause a processor to perform the steps, or may beperformed by a combination of hardware and software. Although a specificorder of method steps may be shown or described, the order of the stepsmay differ. In addition, two or more steps may be performed concurrentlyor with partial concurrence.

The terminology used herein is for the purpose of describing particularaspects only and is not intended to be limiting of the disclosure. Asused herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. It will befurther understood that the terms “comprises,” “comprising,” “includes,”and/or “including” when used herein specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

It will be understood that, although the terms first, second, etc., maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement without departing from the scope of the present disclosure.

Relative terms such as “below” or “above” or “upper” or “lower” or“horizontal” or “vertical” may be used herein to describe a relationshipof one element to another element as illustrated in the Figures. It willbe understood that these terms and those discussed above are intended toencompass different orientations of the device in addition to theorientation depicted in the Figures. It will be understood that when anelement is referred to as being “connected” or “coupled” to anotherelement, it can be directly connected or coupled to the other element,or intervening elements may be present. In contrast, when an element isreferred to as being “directly connected” or “directly coupled” toanother element, there are no intervening elements present.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms used herein should be interpreted ashaving a meaning consistent with their meaning in the context of thisspecification and the relevant art and will not be interpreted in anidealized or overly formal sense unless expressly so defined herein.

It is to be understood that the present disclosure is not limited to theaspects described above and illustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the present disclosure and appended claims. Inthe drawings and specification, there have been disclosed aspects forpurposes of illustration only and not for purposes of limitation, thescope of the inventive concepts being set forth in the following claims.

Table of reference numerals 1 propeller drive assembly 2 hull of marinevessel 3 propeller drive unit 4 propeller 5 first rotational axis 6propeller drive system 7 electric drive means 8 housing 9 first opening(of hull of marine vessel) 10 inner space of housing 11 second opening(of housing) 12 suspension mechanism 13 first longitudinal axis 14control unit 15 sea bottom 16 sea surface 2500 computer system 2502processor device 2504 memory 2506 system bus 2508 non-volatile memory2510 volatile memory 2512 basic input/output system (BIOS) 2514 storagedevice 2516 operating system 2518 program module 2520 computer programproduct 2522 input device interface 2524 output device interface 2526communications interface P0a predetermined rotational position of firstpropeller P0b predetermined rotational position of second propeller M0method of controlling a propeller drive assembly M1 triggering rotationM2 moving P1 stowed position of propeller drive unit P2 deployedposition of propeller drive unit A joint projected driving area Amaxmaximum joint projected driving area Amin minimum joint projecteddriving area P plane orthogonal to first rotational axis

1. A method of controlling a propeller drive assembly attachable to ahull of a marine vessel, said propeller drive assembly comprising apropeller drive unit carrying at least one propeller shaft for carryinga respective propeller for rotation about a first rotational axis,wherein the propeller drive assembly comprises a housing for attachmentto a hull of the marine vessel on an inside of the hull such that thehousing surrounds a first opening of the hull and seals to the hull,wherein the housing defines an inner space and wherein the housing isprovided with a second opening through which at least a portion of thepropeller drive unit is movable into and out of the inner space, andwherein the propeller drive assembly comprises a suspension mechanismattached to the housing and configured to suspend the propeller driveunit, wherein the suspension mechanism is movable along a firstlongitudinal axis of the housing between a stowed position, in which thepropeller drive unit is positioned inside the inner space of thehousing, and a deployed position in which at least a portion of thepropeller drive unit protrudes outside the housing through the secondopening, wherein the method comprises: a first step comprisingtriggering rotation of each propeller shaft such that the respectivepropeller shaft reaches a respective predetermined rotational positionand stops at the respective predetermined rotational position, and asecond step comprising triggering movement of the suspension mechanismfrom the deployed position to the stowed position, wherein eachpropeller shaft is provided with a respective propeller, and wherein therespective predetermined position of each propeller shaft is such thateach respective propeller is at least partly, such as fully, confinedwithin the inner space of the housing when the propeller drive unit isin the stowed position.
 2. A method according to claim 1, wherein thepropeller drive assembly further comprises at least one electric drivemeans configured to control a rotational position of each propellershaft about said first rotational axis and wherein the first stepcomprises triggering the electric drive means to perform the rotation(s)of the respective propeller shaft(s) to the respective predeterminedrotational position(s).
 3. A method according to claim 1, wherein saidpropeller drive unit comprises two propeller shafts each carrying onepropeller wherein the propellers are rotatable relatively each otherabout the first rotational axis such that that a joint projected drivingarea provided by the propellers in a plane perpendicular to the firstrotational axis varies in response to a relative rotation between amaximum joint projected driving area and a minimum joint projecteddriving area together defining a joint projected driving area range, andwherein the predetermined positions are such that the joint projecteddriving area when the propeller shafts are in their respectivepredetermined positions is within a lower 10% of the joint projecteddriving area range or within a lower 5% of the joint projected drivingarea range, or is the minimum joint projected driving area.
 4. A methodaccording to claim 3, wherein the propellers have a same number ofblades.
 5. A method according to claim 1, wherein said second step isperformed after, and/or simultaneously with said first step.
 6. A methodaccording to claim 1, wherein said propeller drive unit comprises twopropeller shafts each carrying one propeller wherein the propellers arerotatable relatively each other about the first rotational axis suchthat that a joint projected driving area provided by the propellers in aplane perpendicular to the first rotational axis varies in response to arelative rotation between a maximum joint projected driving area and aminimum joint projected driving area together defining a joint projecteddriving area range, and wherein the predetermined positions are suchthat the joint projected driving area when the propeller shafts are intheir respective predetermined positions is within a higher 20% of thejoint projected driving area range or within a higher 10% of the jointprojected driving area range, or is the maximum joint projected drivingarea.
 7. A control unit for controlling a propeller drive assemblyattachable to a hull of a marine vessel, said control unit beingconfigured to perform the method according to claim
 1. 8. A propellerdrive system comprising a propeller drive assembly and a control unit,said propeller drive assembly comprising a propeller drive unit carryingat least one propeller shaft for carrying a respective propeller forrotation about a first rotational axis, said propeller drive assemblyfurther comprising a housing for attachment to a hull of the marinevessel on an inside of the hull such that the housing surrounds a firstopening of the hull and seals to the hull, wherein the housing definesan inner space and wherein the housing is provided with a second openingthrough which at least a portion of the propeller drive unit is movableinto and out of the inner space, and wherein the propeller driveassembly comprises a suspension mechanism attached to the housing andconfigured to suspend the propeller drive unit, wherein the suspensionmechanism is movable along a first longitudinal axis of the housingbetween a stowed position, in which the propeller drive unit ispositioned inside the inner space of the housing, and a deployedposition in which at least a portion of the propeller drive unitprotrudes outside the housing through the second opening, wherein eachpropeller shaft is provided with a respective propeller, and, whereinthe control unit is configured to trigger rotation of each propellershaft such that the respective propeller shaft reaches a respectivepredetermined rotational position and stops at the respectivepredetermined rotational position, wherein the control unit is furtherconfigured to trigger movement of the suspension mechanism from thedeployed position to the stowed position, and wherein the respectivepredetermined position of each propeller shaft is such that eachrespective propeller is at least partly, such as fully, confined withinthe inner space of the housing when the propeller drive unit is in thestowed position.
 9. A propeller drive system according to claim 8,further comprising at least one electric drive means configured tocontrol a rotational position of each propeller shaft about said firstrotational axis, wherein the control unit is configured to trigger theelectric drive means to perform the rotation(s) of the propellershaft(s) to the respective predetermined rotational position(s).
 10. Apropeller drive system according to claim 8, wherein said propellerdrive unit comprises two propeller shafts each carrying one propeller,wherein the propellers are rotatable relatively each other about thefirst rotational axis such that that a joint projected driving areaprovided by the propellers in a plane perpendicular to the firstrotational axis varies in response to a relative rotation between amaximum joint projected driving area and a minimum joint projecteddriving area together defining a joint projected driving area range, andwherein the predetermined positions are such that the joint projecteddriving area when the propeller shafts are in their respectivepredetermined positions is within a lower 10% of the joint projecteddriving area range or within a lower 5% of the joint projected drivingarea range, or is the minimum joint projected driving area.
 11. Apropeller drive system according to claim 8, wherein the control unit isconfigured to trigger movement of the suspension mechanism from thedeployed position to the stowed position after, and/or simultaneouslywith said triggering of rotation of each propeller shaft such that therespective propeller shaft reaches a respective predetermined rotationalposition and stops at the respective predetermined rotational position.12. A marine vessel comprising a propeller drive system according toclaim
 8. 13. A computer program comprising program code means forperforming the method of claim 1 when said program is run on a controlunit.